Thermionic tube connecting means



May '10, 1932. v w. L. KRAHL THERMIONIC TUBE (5ONNECTING MEANS Filed Dec. 10. 1927 2 Shee sl SPEAKER ATTORNEY May 10, 1932. w. KRAHL 1,857,646

THERMIONIC TUBE CONNECTING MEANS Filed Dec. 10. 1927 2 Shee sh 2 -INVENTOR MLTE/Z [00/5 /f/f////L 5 m N N ATTORNEY Patented May 10, 1932 .HJMTE- STATES WALTER LOUIS KRAHL, OEMONTGLAIR, NEW JERSEY,:ASSIGNTOR,?"BY' MESNEwA-SSIGN- Mamas, r0 anemones RADIO TUBE conPANY, or NEWABK, NEW ERSEY, A cons POBATION or DELAWARE THERMIONIC TUBE ooniv'riorrue ME NS f Application filed December 10,1'927.f Sena nolasaoavf This invention relates to a thermionic alternating current tube'and method and means of connecting the same in acircuit originally wired for direct current operation. The invention is particularly adaptedfor use in connection with a thermionic tube shown in my application, Serial No. 156,946, entitled Power operated vacuum tube construction and circuit therefor.

In changing a direct current radio set over to alternating current operation, by substituting alternating current tubes for the direct current tubes, it is necessary generally, to somewhat alter the circuit wiring of the set, and particularly the leads which are connected to the filaments of the tubes for energizing the same.

One means for making this change is t provide entirely separate leads for thea'lterq nating current supply and leaving the. direct .current leads as they are in the circuit wlthout using the same. If an alternating current tube is used having contacts on the base corresponding to the contacts of a direct current tube, these tube contacts have sometimes been insulated from the corresponding contact-s of the socket by providing an adapter which has a basesimilar to a tube base to fit into thesocket and a socket adapted to receive the vacuum tube and is provided with intermediate connections so that any desired change in the connections of the tube terminals may be made by means of terminals mounted on the adapter itself. Such adapt.- ers necessarily constitute additional pieces of equipment which increase'the cost of chang ing over a set and have other disadvantages such. as raising the tube with respect to the original socket so that a set designed with limited head-room for the tubes'will be impossible to change over because the added height of the tube will prevent the insertion of the same. a

One of the primary objects of the present invention therefore, is topermit the change of a radio set from'direct current to alternating current operation by the substitution of alternating current tubes without the use of adapters; the tubes being designed to fit into standard sockets.

from the corresponding contacts"- A-battery circuit which is c Another-objeet of theinvention is to pre- Vlde a tube having a base whichmay be readily changed so thatauxiliary filament-terminals may be directly applied to the tube.

Another object of the invention is to provide a tube with removable terminalson the base thereof which may bequickly ande'asily replaced with insulating terminals adapted to electrically separate the filament terminals adapted to receive the tube. 51

' Another object of the' invention is toprovideaconnection'harness with means, to readily attachthesameto the filament'termin'a'ls on a plurality, of tubesfan'd which may be supplied as an aukiliary part of the wiringof a radio" set Another object of 'the invention is to pm Vlde means tof apply anindividual potential 'on the grid of the detectoritube of a radio set of a socket without otherwise changing. the permanent wiring of'the set.

Another object of the inventionii s topro- Vlde' a means for' controlling the volume" of the output of the radio set when the original volume control is" no longer used.

' Other objects and objects relating. to economies of thefcons'truction of various parts will app'ear' as, thedescription of the invention proceeds. 7 f i One embodiment of the inventionhas been illustrated in the accompanying drawings, in which ig. lis a circuit diagram illustrating the application rof my invention;

rinected to Flg. 2 is a plan viewof the harneSsshOW connectedt'o the tubesof a radio set,

Fig; 3 isan elevation of the lower part'of analternating current tube, part of which is shown in section to illustrate. the removable terminals; p

l F ig 3A is an elevation of one ofthe conductorterminals; I

Fig. at is abottom view of an alternating current tube embodying thef'nvention jwith the auxiliary terminals attached Y I v Fig.5 is 'anelevation ofa gridleakshowing the insulating clip attached thereto; V

Figs. 6 and 7 are an'end'view and an elevaall terminals are set.

connection with my invention; and

Figs. 9 and 10 are an elevation and plan vlew, respectively, of a means for connecting the volume control shown in Fig. 8.

In carrying out theinvention, I provide alternating current tubes with removable contact pins in their bases. This is illustrated in Fig; 3 of the drawings wherein the glass envelope 10 is mounted in the usual moulded base 11 in which the plate and grid contact The connections 12 to the filament, however, are brought down to two thimbles 13. which are moulded in the base 11 in the position ordinarily occupied by the filament terminalsand which are drilled and tapped to receive the threaded end 14 of the filamentcontact terminal 15, Fig. 3A. The connection from the filament to the, thimbles is preferably made by providing a hole 16 in the bottom of the base adjacent each thimble 1 and placing one end of a thin fiat conductor or bus-bar 17 adjacent the edge of the hole, the other end ofwhich conductor is provided with an opening 18 large enough to receive easily the threadedvend 14 of the conducting pin 15, but'notas large as the diameter of the pin itself, so that when the pin is screwed in place, it will hold the conductor firmly against ment of the tube preferably passes through,

' lating pin.

the thimble 13. Thewire 12 from the filathe hole 19 and is soldered to the conductor or bus-bar 17 so that the latter is held in place solely by the conducting pin and the soldered connection.

I have provided also insulating pins which may be attached to the base of the tube as indicated in Fig. 3 in place of thejconductor pins. These pins 20 have a threaded end 21 similarly to the conductor pins 14, but the outer end 22 is smaller in diameter, and preferably provided with knurled ridges 23 or otherwise formed irregular on the surface thereof and surrounded by insulating material 24 which may be moulded thereon and which has a diameter substantially the same as the diameter of the conducting pin 15.

The insulating pin 20 when the tube. is placed in a standard fiat socket, insulates the filament terminals of the tube from the corresponding contact terminals ofthe socket and inorder to make the proper connections to the filament terminals of the tube, 1 have provided auxiliary filament terminals 25 which are preferably formed of thin sheet metal such as copper or brass, and constitute a strip 25 hat ing a hole27 in one end substantially the same size as the hole 18 in the connector or bus-bar 17 by whichthestrip V may-be rigidly secured against the t-himble and electrically connected thereto by the insu- The auxiliary terminal is profilament current may be supplied by means of the auxiliary filament terminals.

I Where a plurality of tubes are used in aset, I have found it convenient to connect the two filament terminals 29 and 30 (Fig. 2) of each tube to two wires 31 and 32 respectively, which may have the auxiliary terminals 25 soldered to them at certain properly spaced intervals. Thesetwo wires 31 and 32 shoulc preferably be twisted together and may be included with two other wires 33 and 34, the purpose of which will be explained hereafter, in a cable 35, which may be led outside thecasing for the circuit in order to make the connections to the alternating current source and batteries. 7

"The wire 33 in this cable ha's'one end connected to the wire 32 adjacent the auxiliary terminal 25 which is intended for connection other end of the wire extends out of the opposite end of the cable and forms the connection from the set tothe negative terminal of the B-battery.

It has been found preferable in the operation of the alternating current tube above referred to, to provide the grid of the detector I tube with a positive D bias, while the grid of theamplifier tubes may be charged negatively; If all of the grid returns are connected together, and given a negative potential, it is necessary in some way, to breakthe grid the detector tube in order to procircuit of vide this grid with a positive potential.

order to accomplish this result, I have pro vided an insulating connector 36 whlch 1s preferably formed of a thin fiat metal plate 37 having an opening 38 therein and provided at one side with insulating material 39. The

insulating material '39 may conveniently be formed of a short piece of rubber tube, while afiange 40 around the edge of the opening 38 in the plate form's'a convenient means of attaching the rubber insulator.

This plate may be placed between the end of the grid leak 41 furthest from the detector tube and the support 42 therefor so that the metal plate 37 comes in contact with the grid leak 41, while the rubber tube 39 contacts with the support 42. The other endof the plate 37 is provided with a bent or rolled portion 43 to receive the wire 34 for connecting in the circuit, which wire may be soldered to the plate. When this connector 36 is in place, between the end of the grid leak 41 and the rinse-Bee convenient harness for quickly changing a set.

wired for direct current over to alternating current operation.

Where the grid leak is of the fuse type, having cylindrical metallic ends 44, which are sprung into U-shaped clips, the insulating connector for the grid leak may he formed,

as in Fig. 6, of a flat strip of metal riveted v or otherwise attached to a somewhat wider flat strip 46 of insulating material such as fibre, both of which may be bent around the cylindrical end of the grid leak before it is sprung into the U-shaped clip, the insulating material coming between the clip and the me,- tallic plate of the connector.

The invention is diagrammatically shown adapted to the circuit of a well-known directcurrent receiving set in which the light full lines represent the permanent wiring of the set, while the heavy lines indicate the additional wiring necessary for the use of alter nating current tubes. The auxiliary grid connector 36 is shown connected through the cable 35 to 4 volts positive on the D-battery, while the negative potential is placed on the radio frequency tubes by simple connecting the A-battery terminals of the set together, and to a O-battery of 1 volts. The negative bias on the two audio tubes may be made somewhat larger, if desired, by the addition of more C-battery voltage and I have found in this-instance, that about 27 volts on the last audio stage will give satisfactory results.

It will be noted from an inspection of Fig. 1 that inasmuch as the permanently wired filament connections 47 and 48 are not used withthe present invention, the volume control which comprises a rheostat/l?) is also throw out of service. I have, therefore, found it necessary to provide an auxiliary volume control and such a control comprises a potentiometer 50 connected between the antenna and the ground, while the variable arm 51 of the potentiometer is connected to the antenna terminal on the set. In connecting this volume control into the circuit, therefore, it is necessary only to'disconnect the antenna from the set, connecting the arm of the potentiometer in its place, and then to connect the antenna to one end of the po tentioineter coil and the ground to the other.

end. While such a volume control gives er:- cellent results, any other preferred type may be used, such as a variable resistor 52 of from 0 to 200,000 ohms connected across thesecondary 53 of the radio frequency transform-- er 54 (see Fig. 8) which is connectedtto ground terminal ofthe set. v a

1 It is evidentfrom the above. description t the grid of the, tube. immediately preceding the detector; tube. Aconvenient ;way to; connect: the resistor 52 isto connect one end di- ;rectly tothe grid terminal of the tube..i-mm1ediately preceding,.the detector tubegfThis may be accomplished by meansof aconnector clip 55 shown in Figs. 9 and 10 :whichmay .be providedwith .an'opening 56 to fit over the grid terminal 57 of the tube. ;A plurality of lugs58 may: be left uncut from the opening 56 so that the lugs will be bent down- Wardly when theclip 55 is forced over the end of the terminal .57,'thus insuring a tight connection. Thexe'nd of the clip 55 maybe rolled similarly: to theterminal 25 to forma "socket 59 toreceivethe end of the wireattached to the resistor. The other terminal of the variable resistor maybe connected to the that the invention provides a very convenv ient and efficient method of changing a standard direct current radio set over to alternating current operation in a minimumof time.

being as follows: 7

First, the direct p q from the set second, the filament terminals on the alternating current tubes are replaced The steps. necessary to make such change by the insulating terminals at the same time securing the, auxiliary terminals with ,the harness attached in place at the .base; of [the current tubes are removed tubes, The tubes are thenginsertedin the sockets, the harness cable being led out through; any convenient wire open ng at the back of the set for connection to ,the. transformer 60, the primaryof, which is .c onnect-- ed .to the alternating currentsonrce; The

grid leak connector is 'then slipped between the outer-end of the. grid lea lgand .the sup; port therefor and the Volume control is con} nected between the antenna and the. set. as already describedj. When-the A baItteryterminals of theset are connected together, and

to a negative terminal of a C batte'ry, as indicated .in Fig. 1, andthe other end Lof the grid leak connector to apositive D terminal of the B-battery,the set is ready for'operation. v

i The A. plus lead: of a receiverim ay be in place of the extralead in the cable for the connection to the positive potential in radio sets whereinthis A plus leadis connected tothe detector grid returnandto nov other points in the circuit except the plus filament terminals of the tube sockets} In thiscase a three wire cable would be used. I ;While I have shown and described the in} vention'infcon nection with a specific type of alternating current tubes, and aparti'cu lar structure for. direct current operation, it is evident that the invention may be applicable to any number of different direct current circuits, or other types of alternating current tubes, or it may be applicable in changing one type of direct current circuit to another type of direct current circuit, and I do not desire to limit myself, therefore, to the specific construction shown and described, but to interpretthe invention broadly, within the scope of the appended claims.

. Having thus described my invention, what I claim as new and desire to secure'by Letters Patent is: 7

1. In a connection harness for use in adapting a direct current radio circuit for alternating current operation, a four wire cable, taps on two of said wires adapted to be connected to the filament terminals of the tubes, an insulating clip on the end of a third wire adapted to electrically contact with one'end of a grid leak and insulate said grid leak from its normal support at that end, and having the fourth wire connected to one of the first two wires at a point adjacent the tap for connection to the filament of the detector tu e. r

2. In a connection harness, for use in adapting a direct current radio circuit for alternatring current operation; a cable, two wires-in said cable having taps at spaced intervals thereon adapted to be connected to the filament terminals of said tubes, a third wire in said cable, an insulating clip at the end of said wire adapted to fit between one end of a grid leak and the support therefor and to insulate that end from said support, a fourth wire in said cable connected to one of said first two wires.

3. In a connection harness for use in adapting a direct current radio circuit for alternating current operation, a cable containing a plurality of wires, taps on two of said wires adapted tobe connected to the filament terminals of the tubes, and another of said wires connected to; one of said first two wires at a oint adjacent the tap for connection tothe filament of the detector tube, v V

4. In a harness for use in connecting a direct current radio circuit for alternating current operation, a four wire cable, tapson two of said wires, means to directly connect said taps to the filament terminals of alternating current vacuum tubes, means on said termi nals to insulate said terminals from the con tacts of the socket whenthe tube is inserted therein, and an insulating clip on the end of a third wire adapted to electrically contact with one end of a grid leakand insulate said I grid leak from its normal support at that end, the fourth wire being connected to one of the first two wlres at a point adjacent the tap for connecting the filament of the detector W e. t

' In testimony whereof, I aflix my signature.

WALTER LOUIS KRA'HL; 

